Integrated air foil and diamond flow vane

ABSTRACT

A flow enhancing arrangement for ducts such as rectangular flue ducts wherein a series of tear shaped foils are spacedly mounted in the duct extending from top to bottom thereof and where a series of diamond shaped vanes also extending from the top to the bottom of the duct are spacedly mounted between the tear shaped foils to provide a more uniform flow distribution and to lower the pressure thereby. A series of baffles extending from both the tear shaped foils and the diamond shaped vanes may also be used.

FIELD AND BACKGROUND OF INVENTION

The present invention is generally drawn to devices for distributing andmixing particle or injected gas laden air in ducts and more particularlyto such devices as used in the ducts of power generating stations whichmay contain ammonia for NOx reduction.

It is known to use air foils for distributing and mixing air streams insecondary air supply ducts and selective catalyst reduction (SCR) systemflues (10), as shown in FIG. 1. The usual arrangement comprises aplurality of whole foils (12) in the center of the flue and half foils(14) at the walls (16) of the flue (10). Another example of prior artair foil design is shown in FIG. 2. This is the air foil configurationfor distributing and mixing economizer bypass flue gas used in theKansas City Power & Light, Hawthorn Station in their SCR flue system.This system uses the basic FIG. 1 system but has plates (18) added. Thecontoured lines in the above and the remaining figures which will bedescribed later represent the airflow distribution in the duct (10). Inaddition, air foils (12) have been used extensively for flow measurementand control. It is also known to use Diamond shaped flow devices forflow control with low pressure drop. For example, many commerciallyavailable dampers contain diamond shaped blades. Such devices achievegood flow control with minimal pressure group.

The disadvantage of the above described prior art arrangements are addedpressure loss, potential mixing of ammonia when added, and therequirement of a larger flue to accommodate the system components.

Ammonia injection grids (AIG) with zone control are known and have beeninstalled to distribute a prescribed rate of ammonia for NOx reducingSCR systems. Static mixers are commercially available in several formsand have been proposed to reduce thermal and/or flue gas speciesgradients by adding turbulent mixing in SCR flue systems. Koch andChemineer are manufacturers that produce some such commerciallyavailable static mixers.

Design requirements for secondary flues and SCR systems include thespecification of flow distribution and thermal gradients downstream ofthe mixing device(s). The objectives are to achieve flow uniformly andminimize thermal gradients. For example, in an SCR system mixing andflow uniformity at the ammonia injection grid should be sufficient suchthat catalyst performance and life is maintained. To accomplish thesegoals, devices such as those listed in the prior art have been utilized.While it is also desirable to minimize the unrecoverable pressure lossto the system, space restrictions limit the installation of an air foilfor gas mixing and a separate AIG for ammonia distribution in an SCRsystem. Thus a uniform distribution system for such applications wasneeded which would also minimize the pressure loss therein.

SUMMARY OF INVENTION

The present invention solves the problems associated with prior artdevices as well as others by combining the best features of the priorart mixing foils and diamond shaped flow device to yield an integrateddevice that provides an improved system design. The present invention isunique because it combines air foils and diamond vanes to produce adevice that provides a uniform flow distribution with minimal pressuredrop. As noted, both air foils and diamond vanes have been usedseparately to accomplish flow control, however, these systems have notbeen used together in a manner proposed in the present invention.

In another embodiment of the present invention, plates or baffles areadded to both the mixing foils and the diamond shaped devices to producea uniform flow and low pressure drop device especially adapted for fluegas applications.

In view of the foregoing, it will be seen that one aspect of the presentinvention is to provide mounted device for improved uniformity of flowdistribution.

Another aspect of the present invention is to provide a duct mounteddevice for reduced pressure drop in the duct.

Another aspect of the present invention is to provide a flue ductmounted device for improving flow distribution and lowering the pressuredrop therein.

These and other aspects of the present invention will be more fullyunderstood upon a review of the following description of the preferredembodiment when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a prior art foil arrangement for ducts.

FIG. 2 is a prior art foil and plate or baffle arrangement for flueducts.

FIG. 3 is a foil and diamond arrangement of the present invention forducts.

FIG. 4 is another embodiment of the present invention using a foil anddiamond arrangement with divider plates.

FIG. 5 is a side view of the foil and diamond arrangement seen in FIG. 3and FIG. 4.

FIG. 6 is a rear view of the foil and diamond arrangement of FIG. 5.

FIG. 7 is a front view of the foil and diamond arrangement seen in FIG.5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and more particularly to FIGS. 3 and 5-7, animproved flow system duct arrangement is shown which integrates the airfoils (12) with diamond shaped flow vanes (20). Flow uniformlydownstream of the foil throats is achieved with the arrangement. Acomparison of the distributors with and without the diamonds (20) (FIGS.1, 2, vs. FIG. 3) clearly demonstrates the improved flow distributionwith the diamonds (20). The aerodynamic shapes of the diamonds (20) andairfoils (12) are also advantageous to the design objective ofminimizing system unrecoverable pressure loss. The advantage existswhether or not the foils (12) will be used or particle injection forreducing NOx due to their aerodynamic shape which is exposed to the gasstream. Thermal gradients are also minimized by distributing the fluegas for temperature control over the cross section of the flue.

For SCR applications with ammonia injection between the foils (12),mixing of ammonia with the flue gas is improved because of the flowuniformity provided with the additional use of the diamond vanes (20).

An alternative arrangement to the invention is shown in FIG. 4 whereinplates or baffles (18) are mounted to both the foils (12) and thediamonds (20). The baffles (18) from the diamonds (20 extend across thespace of the foils (12). This arrangement promotes flow uniformitybetween the foils (12).

As seen from FIGS. 5-7, the duct (16) is rectangular and the foils (12)and diamonds (20). Both extend from the top to the bottom of the duct(16). The foils (12) are tear-shaped having a rounded end (19) and asharp end (21). The baffles or plates (18), when they are used, alsoextend from the top to the bottom of the duct starting at imaginarylines (22, 24) of the rounded end (19) of the foils (12) and leadingedges (23) of the diamonds (20) respectively. The plates (18) are shownin dotted lines at FIG. 5 as alternate embodiments.

Certain modifications and additions will occur to those skilled in theart area upon reading this disclosure. It will be understood that allsuch were deleted herein for the sake of conciseness and readability butare intended to all with the scope of the following claims.

1. A flow enhancing arrangement for ducts having fluid flow thereincomprising: a series of tear-shaped foils spacedly extending across theduct; and a series of diamond shaped vanes shapedly extending betweensaid series of tear-shaped foils.
 2. A flow enhancing arrangement forducts as set forth in claim 1 including a series of baffles extendingfrom said tear shaped foils and from said diamond shaped vanes.
 3. Aflow enhancing and arrangement for ducts as set forth in claim 2 whereinsaid tear-shaped foils have a rounded end and a sharp end and whereinsaid baffles extend from said rounded end of said foils.
 4. A flowenhancing arrangement for ducts as set forth in claim 1 wherein saiddiamond shaped vanes have sharp front and back ends and said bafflesextend from said front end.
 5. A flow enhancing arrangement for ducts asset forth in claim 1 wherein said tear-shaped foils have a rounded endand a sharp end and wherein said baffles extend from said rounded end ofsaid foils.
 6. A flow enhancing arrangement for ducts as set forth inclaim 5 wherein said diamond shaped vanes have sharp front and backends.
 7. A flow enhancing arrangement for ducts as set forth in claim 5wherein the duct is a rectangular flue duct.